Monday, 30 September 2019

Mapping Mountains – Summit Relocations – 100m Twmpau and Y Trechol – The Dominant Hills of Wales


Cock Hill (ST 153 750)

There has been a Summit Relocation to a hill that is listed in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cock Hill (ST 153 750)

The criteria for the two listings that this summit relocation applies to are:

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3rd December 2015.

The name of the hill is Cock Hill and it is adjoined to the Bro Morgannwg group of hills, which are situated in the southern part of South Wales (Region C, Sub-Region C2), and it has the A4232 road to its north and east and a minor road towards its south, and has the city of Caerdydd (Cardiff) towards the north-east.

When the original Welsh 100m P30 list was published on Geoff Crowder’s v-g.me website this hill was listed with a c 115m summit height positioned at ST 153 750, based on the uppermost ring contour that appears on contemporary Ordnance Survey 1:25,000 Explorer maps which takes in a triangulation pillar with an adjoining flush bracket height of 115.345m positioned at ST 15338 75022.

Extract from the Ordnance Survey 1:25,000 Explorer map

The details for this hill were re-evaluated when the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online, and as this map gives no further details the summit location remained the same.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

LIDAR summit image of Cock Hill

The summit height produced by LIDAR analysis is 115.6m positioned at ST 15303 75089 with LIDAR also giving a 115.7m height positioned at ST 15310 75062 to a raised field boundary that is excluded from the height of this hill as it is considered a recent man-made construct and with the natural summit of the hill positioned in a different field compared to where the summit was originally listed.  The above detail comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to any listed hill whose summit meets the following criteria; where there are a number of potential summit positions within close proximity and the highest point is not where previously given, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist, or when the summit of the hill is in a different field compared to where previously given, or when the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct.

Therefore, the summit height produced by LIDAR analysis is 115.6m to ground meeting the criteria used within this list and this is positioned at ST 15303 75089, this is in a different field to the previously listed summit position and is approximately 80 metres north-westward from it and approximately 28 metres from where the highest part of the raised field boundary is situated, and as the latter is considered a relatively recent man-made construct it is not taken as a part of the height of this hill.


The full details for the hill are:

Group:  Bro Morgannwg

Name:  Cock Hill

OS 1:50,000 map:  171

Summit Height:  115.6m (LIDAR, natural summit)

Summit Grid Reference (new position):  ST 15303 75089 (LIDAR, natural summit)

Bwlch Height:  46.3m (LIDAR)

Bwlch Grid Reference:  ST 13392 74714 (LIDAR) 

Drop:  69.3m (LIDAR)

Dominance:  59.92% (LIDAR)


Myrddyn Phillips (September 2019)



Sunday, 29 September 2019

Mapping Mountains – Trimble Surveys – Glyder Fawr


06.07.19  Elidir Fawr (SH 611 612), Foel Goch (SH 628 612), Mynydd Perfedd (SH 623 618), Carnedd y Filiast (SH 620 627) and Fronllwyd (SH 617 631)  

Elidir Fawr (SH 611 612)

Having arrived at the end of the paved public road that makes its way toward the Marchlyn Mawr Reservoir, Aled and I sat in the car for almost two hours watching the constant drizzle and low cloud envelop the land.  The drizzle soon developed in to rain and the thought of heading out in these conditions did not enthuse me.  However, as the forecast predicted better conditions late morning and clearing for the afternoon we eventually donned our waterproofs and headed over the locked gate to the continuation of tarmac that led forever upward toward the reservoir and low cloud.

We had prepared for another survey, but with the ground so wet and the cloud base low, we decided that conditions were not favourable and this particular hill could wait for another day and a round taking in Elidir Fawr and ending on Fronllwyd was feasible.

The paved road ends at the Marchlyn Mawr Reservoir and from here we joined the narrow path that ascends the northern ridge of Elidir Fawr.  The circuit ahead of us used to be one that I did frequently and always enjoyed, as it includes five hills and gives variety and good views, today with clag on the hill we were in no rush and slowly plodded our way up in to the mist, eventually cresting the hill’s eastern ridge close to the summit.  Here we came upon two marshals who were a part of the Snowdonia Seven which is the most challenging sporting event in the Police’s calendar.  We stood and chatted with them; a father and daughter, for a number of minutes, they explained that the leaders had just passed by, soon the next group of four competitors appeared and headed further in to the mist toward the top of Elidir Fawr.  We also soon followed.

The summit of Elidir Fawr has a large wind shelter on its ridge with the high point further south-west and crowned by an untidy cairn.  Positioned in the wind shelter Aled used an Abney level to confirm the highest rock and within a couple of minutes the Trimble’s internal antenna was aligned with it and gathering its customary five minutes of data.

Gathering data at the summit of Elidir Fawr

I’d come prepared with a series of ten figure grid references for each summit and bwlch that we may visit, and having packed the Trimble away we headed back toward the two marshals as more teams of four kept appearing through the mist on their way toward the summit of Elidir Fawr.  Our next point to survey was the connecting bwlch ahead of us; this is named Bwlch y Marchlyn on Ordnance Survey maps and is adjoined to Carnedd y Filiast.  The main path heading toward it contoured around the upper part of Cwm Dudodyn missing the castellated crest of the ridge and the actual bwlch, and initially so did we in the mist, when close to it we scrambled up a steep mudded gully and checked the grid reference in the Trimble, the critical point of the bwlch was a few metres behind us and thankfully relatively open for satellite reception and easy to position the Trimble on.  As it gathered data I stood on the northern part of the narrow ridge overlooking steep ground plunging down toward the reservoir, happy in the knowledge that progress was being made even though the weather conditions were not ideal.

Gathering data at the bwlch of Carnedd y Filiast

Once I re-joined Aled we continued on the main path around the upper cwm toward our next hill; Foel Goch, which rears up steeply from this vantage point, however all we could see were dark misted shapes with outlines of hills and crests of near ridges. 

On our way toward Foel Goch the first signs of rising mist started to develop as land appeared, this gave us a chance to assess where the critical bwlch for Elidir Fawr was placed; this is positioned at the north-western base of Foel Goch and beside the ridge fence as the drop plunges down to Nant Ffrancon.  Leaving the bwlch survey for afterward we continued toward our next hill.

A very grey looking Bwlch y Marchlyn

Just as we started the ascent of Foel Goch, Aled helpfully informed me that we had almost 400ft of uphill immediately above us.  I put my head down, reached a trance like state and very slowly plodded up.  My pace was extremely slow but I managed the whole uphill without stopping, which pleased me.  At the top we came upon two other marshals and very soon a number of other participants in the Snowdonia Seven, unfortunately the marshals were now sweeping up the stragglers with many who appeared on the top of Foel Goch having been timed-out from the challenge.

I’d always accepted the small cairn close to the shear drop on the northern end of the summit ridge of Foel Goch to be at its high point, it isn’t, although it was Trimbled.  The summit is a few metres away to the south, and this was also Trimbled.  During this Aled went hunting for alpine plants and showed me a dwarf tree, related to the willow and no more than delicate green leaves dewed by drizzle and nestled against the ground.

The first data set beside the small cairn atop the summit of Foel Goch


Gathering data at the summit of Foel Goch

As we left Foel Goch the mist started to rise again, giving views toward Elidir Fawr and the bwlch below and the land beyond comprising the summit of Mynydd Perfedd.  It looked as if the conditions were now improving and the rest of the walk would be free of cloud.  Unfortunately the mist soon descended again and kept us in its grip for a while longer.  However, we did have chance to assess the lay of land for the bwlch at the north-western base of Foel Goch which is the one adjoined to Elidir Fawr, and a further Trimble data set was gathered from it.

At Bwlch y Brecan with Mynydd Perfedd in the background


Gathering data at the bwlch area of Elidir Fawr


Foel Goch from Bwlch y Brecan

A path heads from this bwlch steeply up to the summit of Mynydd Perfedd and I slowly followed Aled and joined him beside the spike of rock a few metres from a large wind shelter which constitutes the high point of this hill.  We soon devised an ingenious way to position the Trimble so it was secure and aligned with the highest part of the spike of rock and stood beside the wind shelter as it gathered its all-important data.

An ingenious way to gather data at the spike of rock signifying the high point of Mynydd Perfedd

Beyond Mynydd Perfedd are the higher Carnedd y Filiast and the lower Fronllwyd, I’d wanted to survey these hills and also the ones we had already visited ever since getting the Trimble, but especially Mynydd Perfedd to establish an accurate drop value for the hill and to establish an accurate height for Fronllwyd; a hill that I had previously surveyed many times but always for its drop value and up until today never for its height.

We surveyed two points for the bwlch position of Mynydd Perfedd with the second obviously lower than the first, but as it was still misty when we arrived at the first point we did not realise this until collecting data and packing the Trimble away, as we headed on the continuation of the path toward Carnedd y Filiast the mists started to rip apart and ahead of us was obvious lower ground.

Gathering data at the bwlch of Mynydd Perfedd


The mists start to clear on Mynydd Perfedd

Only two summit surveys remained and the first consisted of a large rock amongst the untidy cairn atop Carnedd y Filiast.  After Aled had used the Abney level to pinpoint the highest rock I set the Trimble up and looked beyond the wind shelter where Aled was now sitting as the distant view further west opened up, and after being in mist for most of our walk the view was to be savoured.

Gathering data at the summit of Carnedd y Filiast

Leaving the summit of Carnedd y Filiast we followed the path down to the connecting bwlch with Fronllwyd, this hill was the first that John, Graham and I surveyed as a threesome using John’s level and staff to do so, and it was one of two hills that I lobbied John and Anne Nuttall to survey as the measurements I had ascertained gave the hill over 15m of drop.  They only accepted its inclusion in their list after the line survey, although it had already entered the list of Welsh hills at and above 500m in height that have 15m minimum drop which is now co-authored with Aled.

As Fronllwyd had been line surveyed for drop its summit only required an accurate height and therefore the bwlch was not Trimbled.  The summit comprises a pointed large rock that can easily be stood on top of, but proves a little awkward to backtrack down from.  I balanced a rock on the upper part of the summit rock, made sure it remained in place and proceeded to balance the Trimble on it with its internal antenna fixed to the very highest part of pointed rock.  It proved a delicate balancing act and one that would not have been attempted if there was any breath of breeze, thankfully there was none and the Trimble remained in place beeping away seemingly floating and aligned all at once.  Needless to say I took many photos!

Gathering data at the summit of Fronllwyd


The Trimble delicately balanced on the high point of Fronllwyd with Elidir Fawr in the background

As we waited for the Trimble to gather its allotted data blue skies appeared with high wisps of cloud and a vivid hue to the emerging colour.  Carnedd y Filiast now shone back radiant in the early evening light, as did Elidir Fawr as the last vestiges of cloud were ripped from its summit.

Carnedd y Filiast

It is always wonderful to be on a summit after hours spent in mist when it clears and views open, but today with the vividness of colour and evening warmth it proved magical.

After packing the Trimble away we joined the narrow path leading down the southern slopes of Fronllwyd to the paved road close to Marchlyn Mawr Reservoir for our easy walk back to Aled’s awaiting car.


Postscript 

Since visiting these hills full LIDAR coverage is now available.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height and positional data that is now freely available for England and Wales.  Consequently the numerical details for these hills have been analysed using this technique, resulting in the LIDAR height and position being prioritised for some of these hills.




Survey Result:



Elidir Fawr
  
Summit Height:  922.3m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 61172 61288 (Trimble GeoXH 6000)

Bwlch Height:  711.1m (LIDAR)

Bwlch Grid Reference:  SH 62566 61555 (LIDAR)

Drop:  211.2m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  22.90% (Trimble GeoXH 6000 summit and LIDAR bwlch)






Foel Goch

Summit Height:  831.0m (converted to OSGM15, Trimble GeoXH 6000)

Summit Grid Reference:  SH 62861 61200 (Trimble GeoXH 6000)

Bwlch Height:  754.0m (LIDAR)

Bwlch Grid Reference:  SH 62711 60231 (LIDAR)

Drop:  77.0m (Trimble GeoXH 6000 summit and LIDAR bwlch)

Dominance:  9.27% (Trimble GeoXH 6000 summit and LIDAR bwlch)






Mynydd Perfedd

Summit Height:  812.8m (converted to OSGM15)

Summit Grid Reference:  SH 62319 61877

Bwlch Height:  792.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 62267 62382


Dominance:  2.51%






Carnedd y Filiast

Summit Height:  823.6m (converted to OSGM15) (significant height revision)

Summit Grid Reference:  SH 62040 62733

Bwlch Height:  744.4m (converted to OSGM15)

Bwlch Grid Reference:  SH 61995 61535

Drop:  79.1m 

Dominance:  9.61%







Summit Height:  720.8m (converted to OSGM15)

Summit Grid Reference:  SH 61747 63161

Bwlch Height:  704.6m (relative to Trimble summit and line survey for drop)

Bwlch Grid Reference:  SH 61858 63028 (LIDAR)

Drop:  16.1m (line survey)

Dominance:  2.24%







Saturday, 28 September 2019

Mapping Mountains – Significant Name Changes – 100m Twmpau and Y Trechol – The Dominant Hills of Wales


Cock Hill (ST 153 750)

There has been a Significant Name Change to a hill that is listed in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Cock Hill (ST 153 750)

The criteria for the two listings that this name change applies to are:

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3rd December 2015.

The hill is adjoined to the Bro Morgannwg group of hills, which are situated in the southern part of South Wales (Region C, Sub-Region C2), and it has the A4232 road to its north and east and a minor road towards its south, and has the city of Caerdydd (Cardiff) towards the north-east.

The hill originally appeared in the 100m P30 list on Geoff Crowder’s v-g.me website under the name of Leckwith Hill, which is a name given a farm positioned to the south-east of the summit on contemporary Ordnance Survey 1:25,000 Explorer maps, and with an accompanying note stating; aka Cock Hill.



Leckwith Hill
115c
171
151
aka Cock Hill.

 

During my early hill listing I paid little regard to name placement on the map, or the meaning of names and to what feature the name was appropriately applied to.  Therefore I prioritised names for listing purposes that I now understand are either inappropriate or where another name is viewed as being more appropriate.

Extract from the Ordnance Survey 1:25,000 Explorer map

Since publication of these P30 lists on Geoff Crowder’s v-g.me website there have been a number of Ordnance Survey maps made available online, some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website, whilst others are current and digitally updated such as the Vector Map Local hosted on the Geograph website, and which is entitled the Interactive Coverage Map.  In the case of this hill it is the series of Ordnance Survey Six-Inch maps that show the placement of the name Cock Hill to be prioritised indicating that it is applicable to the whole area of the hill, whilst that of Leckwith Hill is applicable to a farm positioned to the south-east of the summit.

Extract from the Ordnance Survey series of Six-Inch maps

Therefore, the name this hill is now listed by in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales is Cock Hill, and the confirmation of the placement of this name was derived from the series of Ordnance Survey Six-Inch maps. 


The full details for the hill are:

Group:  Bro Morgannwg

Name:  Cock Hill

Previously Listed Name:  Leckwith Hill 

OS 1:50,000 map:  171

Summit Height:  115.6m (LIDAR, natural summit)

Summit Grid Reference:  ST 15303 75089 (LIDAR, natural summit)

Bwlch Height:  46.3m (LIDAR)

Bwlch Grid Reference:  ST 13392 74714 (LIDAR) 

Drop:  69.3m (LIDAR)

Dominance:  59.92% (LIDAR)


Myrddyn Phillips (September 2019)